Large-area washer having friction increasing elements on the underside thereof

ABSTRACT

In a large-area washer (1) there is an aperture for the insertion of a fastener and a bead (16) to stiffen the washer (1). To provide better engagement with a plate and/or web to be fastened, there are engagement components (13) on the underside of the washer (1) which are pressed out of the whole material of the washer (1) and project approximately perpendicularly downwards from it. The engagement components (13) are conical or truncated cones.

BACKGROUND OF THE INVENTION

The invention relates to a large-area washer with an opening forinserting a fastener, which has protruding meshing elements at thesurface pointing in the fastening direction, which elements increase thefriction or meshing with a panel and/or sheet to be fastened.

Such a washer, which is known from the European patent application EP 0283 184 A1 has, on its underside, as meshing elements, molded pins thatare conically pointed. In another known large-area washer, meshingelements are provided that are embodied as conical points, which arealso produced in conjunction with the manufacture of the washer (U.S.Pat. No. 4,987,714). In both cases, relatively thick plastic washers areat issue. The provision of other forms of meshing elements on theunderside of such plastic washers which, however, may be produced onlyby an injection-molding process, is also known (U.S. Pat. No.5,069,589).

In the case of one known large-area metal washer, such meshing elementsare formed of brackets stamped out of the whole material of the washerand pressed downward, such that these brackets, in frontal view, areembodied in each case, in triangular shape and are oriented with adownward point (U.S. Pat. No. 4,763,456). The triangular brackets dogrip relatively well into insulation or roofing sheets, which are to befastened. However, a serious disadvantage is presented by the fact thatthe brackets, which are bent downward, constitute knife blades of a sortwhen the corresponding forces act upon the roofing sheet, thusdestroying the roofing sheet. As soon as no more than a very small cutis produced in the roofing sheet, no great tensile forces are requiredany longer to pull the roofing sheet out from under the washer. Suchtensile forces on the roofing sheet often result from the effects of thewind, particularly in the case of flat roofs.

Washers having a large area are usually used on a solid underlyingstructure to fasten single layer or multi-layered roofing sheets and/oran insulation layer. The forces arising between the roofing sheet andthe underside of the washers are relatively high and result, inparticular, when the danger exists that the roofing sheet underneath thefastener or under the washer will be pulled out due to correspondingsuction stresses. This tensile stress on the roofing sheet occurstransverse to the axis of the screw, that is, parallel to the plane ofthe large-area washer. The retentive force of downward bent, blade-likebrackets is too slight, so that the roofing sheet, which is, in eachcase, attached in the area of the edge, is torn out underneath thewasher.

A large-area washer, which is intended to extend beyond the contactingedges of two sealing coating sheets is already known (DE-A-29 30 993).The two end regions of this washer have, in each case, a through hole,at the edges of which gripping teeth that constitute gripping organs areembodied. In this instance, relatively large holes are stamped out, suchthat the edge areas of these holes are bent downward as individualpointed brackets.

Such an embodiment would also not lend itself well to absorbingcorrespondingly large suction forces acting on the roofing sheet, due tothe fact that the gripping teeth grip into the roofing sheet with aninsufficient degree of strength or, if they do engage properly, functiononce again as blades, which cause a separation of the sheet in responseto tensions parallel to the plane of the washer.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to create alarge-area washer of the type mentioned at the outset, which provides anoptimal holding of the panel and/or sheet to be attached, without therisk that the panel or sheet will be cut by an appropriate force.

Pursuant to the invention, this objective is accomplished owing to thefact that several pointed meshing elements, pressed from the fullmaterial of the washer and oriented at least approximatelyperpendicularly to the plane of the washer, are provided, which areconnected at least across a partial area of their length ascircumferentially closed conical bodies, truncated conical bodies,pyramidal, truncated pyramidal, cylindrical, or prismatic bodies.

By these means, as is otherwise customary only in the case of plasticwashers, downward oriented, pointed meshing elements are created, whichbring about a good meshing with the roofing sheet or a panel that is tobe secured, yet prevent or do not promote, a cutting up of the roofingsheet. Due to the inventive measure, the possibility exists that thewasher, with its meshing elements, can mesh with a roofing sheet,without cutting any fiber reinforcement that may be present in theroofing sheet.

The meshing elements, of particular construction, pressed from the fullmaterial of the washer, do not result in cutting edges of any kind,which could damage a sheet.

A potential, particular embodiment resides in the fact that the meshingelements are constructed in the form of cup-like depressions pressedfrom the full material of the washer. Through deformation with anappropriate counteracting tool, by deep drawing at the desired sites ofthe large-area washers, an appropriate number of meshing elements can beproduced, while the formation of cutting edges is entirely precluded asa result of the circumferentially closed conical, truncated conical,pyramidal, truncated pyramidal, cylindrical, or prismatic form. Thus,even when large-area metal washers are used, it is possible to create,in a particular manner, an effective meshing element, without the dangerof cutting the roofing sheet under load.

It is entirely possible that the free ends of the meshing elements, thatis, the areas of their points break up slightly, even as the meshingelements are manufactured. However, such a construction can be broughtabout deliberately, if the meshing elements have, at their free end, anaxial diameter, which is relatively small in relation to the diameter attheir foot. By these means, a corresponding roughening or a sharp-edgedregion, which increases the friction relative to the panel and/or thesheet that is to be fastened, and also, an improved meshing with thepanel or the sheet results particularly in the region of the meshingelements. Nevertheless, an effective cutting edge parallel to the planeof the washer is not created.

In the case of a different embodiment, it is proposed that the wallthickness of the meshing element decrease constantly from the foot tothe freely protruding end. Such a variation exists particularly when thesolid material is pressed through with an appropriate counter mold and apressing die. This has an additional positive side effect in that themeshing elements become somewhat more elastic in the direction of theirfree end and, as a result can absorb large forces more easily.

In this regard, it is advantageous if, in the case of a conical meshingelement, the outer conical angle is 50° to 90° and preferably 65° to 80°and the inner conical angle is 30° to 50° and preferably 35° to 45°.Precisely this particular magnitude of the conical angle brings about anoptimal meshing with the roofing sheet or panel to be secured, such thata cutting effect nevertheless being precluded. Similar angles can alsobe provided for a pyramidal meshing element.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the invention are explained in greater detail in thefollowing by means of the drawings, in which

FIG. 1 shows a section though an example of a large-area washer inconjunction with fastening layers of insulation and roofing sheet;

FIG. 2 shows the same example as FIG. 1; however, corresponding forcesare acting on the roofing sheet;

FIG. 3 shows a plan view of a washer from above;

FIG. 4 shows a section along the line IV--IV in FIG. 3;

FIG. 5 shows a section along the line V--V in FIG. 3;

FIGS. 6 to 9 show different embodiments of meshing elements in therepresentation of section A in FIG. 4 on an enlarged scale.

DESCRIPTION OF PREFERRED EMBODIMENTS

A large-area washer 1 is used to fasten an insulation layer 2 and aroofing sheet 3, covering this, on a solid substructure 4. A fastener 6,which in this case is constructed as a screw, is introduced into theopening 5. The roofing sheet 3 is fastened at the edge region 7, theedge region 8 of the subsequent roofing sheet 3' covering the screwingsites. The roofing sheets 3 and 3' are then glued or welded together inthe region 9. The fastening itself, is thus placed in a region, which issealed off from the outside.

If now, as can be inferred from FIG. 2, the roofing sheets 3, 3', arepulled up by suction forces acting in the direction of arrow 10, thencorresponding forces act on the screwed connection and particularly onthe washer 1. The region of the washer 1, on the right hand side in theFigure, is pulled upward in the direction of arrow 11, whereas, theregion of the washer 1 in the left hand side of the drawing is pusheddownward, in the direction of arrow 12. This edge region of the roofingsheet 3 is now to be held securely under the washer 1 in the case ofsuch an extreme attack of forces. For this purpose, a specialarrangement and construction of the meshing elements 13, provided at theunderside of the washer 1, is required and will be explained in greaterdetail below by means of FIGS. 3 to 8. In the embodiment shown in FIG. 3in plan view, the washer 1 is constructed as a elongated rectangle. Ofcourse, square washers or washers with a different exterior shape, suchas that of an ellipse can also be used in the same way. The centralopening 5, for inserting the fastener 6 is constructed in a depression14 of the washer 1; the head 15 of the fastener 6 can be disposed incountersunk fashion due to this depression 14. A peripheral bead 16,serves to stiffen the washer so that a corresponding contacting pressurecan be exerted over a large surface. The course or the arrangement ofsuch a bead 16, or several such beads, can be accomplished in variousways, which have no significant relationship with the meshing elements13. FIGS. 3 and 4 show downwardly bent brackets 17, the purpose of whichis to hold washers, which are stacked on top of one another at anappropriate distance, so that the stacked washers can be singled in asimple manner.

What matters in the case of such large-area washers is how the frictionof mutually contacting surfaces of the washer and of the panel and/orsheet to be fastened can be increased and how a meshing with a paneland/or sheet to be fastened can be improved. In the case of the washerdescribed here, special meshing elements 13 are provided. These meshingelements 13 are pressed out from the full material of the washer 1, sothat pointed, meshing elements 13, aligned at least approximately to theplane of washer 1, are formed. The most important measure lies thereinthat the meshing elements 13 are constructed, at least over a portion oftheir length, as peripherally closed conical, truncated conical,pyramidal, truncated pyramidal, or prismatic bodies. In other words, anessentially triangular bracket is not just simply bent downward to formthe meshing element, as was customary up to now; instead, an meshingelement 13 is created, which has a construction and action similar tothat of a fully cast or injection-molded conical point.

As may be inferred, for example, from FIG. 9, the meshing elements 13,are constructed from cup-like depressions 18, which have been pressedthrough from the full material of the washer 1. In such a stampingprocess, appropriate counter-tools are available for being able toachieve such an outwardly closed form after a deep drawing process.

In most cases, it makes sense if the meshing elements 13 have at theirfree end a relatively small axial opening 19, which is constructedparticularly small in relation to the diameter at the foot of meshingelements 13. Especially when the meshing elements 13 are produced bydeep drawing process, it is advantageous to provide appropriate anglesmatched to a particular effect of the meshing elements 13 in relation tothe roofing sheet that is to be held. By these means, it is alsoachieved that the wall thickness S of the meshing element decreasessteadily from the foot to the freely protruding end and that the freelyprotruding ends of the meshing elements 13 are somewhat more yieldingthan the regions immediately at the foot of the meshing elements 13. Forexample, the inner conical angle W1 is approximately 40° for the twoembodiments of FIGS. 7 and 8. The outer conical angle W2 isapproximately 70° for the embodiment of FIG. 7 and approximately 75° forthe embodiment of FIG. 8. Advisably, the inner conical angle W1 is ofthe order of 30° to 50° preferably 35° to 45° and the outer conicalangle W2 is of the order of 50° to 90° and preferably of 65° to 80°.

For the construction of FIG. 6, the wall thickness S is practicallyconstant over the whole length, with the exception of the direct freeend of the meshing element 13. The production of such a variation by astamping process is also conceivable, in which case, the free end regionof the meshing elements 13 so formed burst open slightly, so that aroughening or corresponding cracks, which increase the friction, areformed or form at the free end of the meshing elements 13. In the caseof the embodiment of FIG. 8, it can be seen that a wave-shaped ortoothed limiting edge, which in turn ensures a specialfriction-increasing effect when used in the roofing sheet, is formed atthe free end of the meshing element.

From the geometry alone, it can be seen that the construction of suchquite special meshing elements 13 can be used not only for large-areawashers made from metal, but also for washers produced from plastic byinjection molding.

In the case of the embodiments shown in FIGS. 6 to 9, the meshingelements 13 are peripherally closed practically over their whole length.It would also be conceivable to construct only the foot region of themeshing elements peripherally closed, the remaining region up to thefree end being divided up intentionally or due to the requirements ofthe material into individual brackets, which continue to form aperipherally closed total form, with the exception of the narrow slotslying in between. It would also be conceivable to provide slots or tearsin the foot region of the meshing elements, that is, in the transitionregion from the planar section of the washer to the slots or crackscorresponding to the meshing element, which then contribute practicallyat the outer wall of the meshing elements 13 to an increase in frictionrelative to the sheet to be fastened. Even though corresponding cracksor slots would then be present, no cutting edge-like constructions wouldresult at the meshing elements 13.

In order to make good penetration of the meshing elements into the paneland/or sheet to be fastened possible, meshing elements 13 advantageouslyare constructed, which consist of a circumferentially closed conical,truncated conical, pyramidal, or truncated pyramidal body. It is,however, also possible to construct the meshing elements in the form ofa cylindrical or prismatic body, in which case, however, the penetrationbehavior into the panel and/or sheet to be fastened would be inferior.However, especially due to the special construction at the free end ofsuch a meshing element, there can be a significant increase in friction,which, in turn, makes possible a particularly effective large-areawasher.

What is claimed is:
 1. A large-area washer for attaching roofing sheetsand/or insulation and having an opening for inserting a fastener,comprises:protruding meshing elements pointing in a fastening direction,said meshing elements being used to increase at least one of frictionand meshing with a panel and/or sheet to be fastened, several saidmeshing elements extending from a generally planar surface of the washerand oriented at least approximately perpendicularly to the planarsurface of the washer, said meshing elements each having a footgenerally at said planar surface and a free end, a hole extending withinsaid meshing element from said foot and through said free end, wherein awall thickness of said meshing elements decreases from said foot to saidfree end and an outer conical angle (W2) of said meshing elements is ina range of approximately 50° to 90° and an inner conical angle (W1) isin a range of approximately 30° to 50°.
 2. A washer as in claim 1,wherein said hole in each said meshing element is small at said free endrelative to a hole dimension at said foot.
 3. A washer as in claim 1,wherein the outer conical angle of said meshing elements is in a rangeof approximately 65° to 80°.
 4. A washer as in claim 1, wherein theinner conical angle of said meshing elements is in a range ofapproximately 35° to 45°.
 5. A washer as in claim 1, wherein said holehas a generally closed circumference at said free end.
 6. A washer as inclaim 1, wherein said hole at said foot has a generally closedcircumference.